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The church was begun in 1226-1265, but was enlarged in the 14th century resulting in the Gothic appearance it has now. However, aspects of the Gothic structure were subsequently destroyed by fires in 1443, 1456 and 1531, and further damage later resulted from military occupation (1548-1552).

It is a large edifice built, like many contemporary edifices of the mendicant orders, in bricks, with a lofty bell tower on the left (this was reduced in height after an earthquake in 1798). The interior is on the Egyptian cross plan with a huge nave covered by trusses and with a transept featuring high chapels.

This is an old praying place of Dominican nuns, connected to numerous episode of sanctity of Catherine of Siena's life. It houses the Canonization of St. Catherine by Mattia Preti, flanked by two 1602 paintings by Crescenzio Gambarelli. Other works by the latter are also present. The main wall has a portrait of St. Catherine.

The altars on the right side are decorated by a Appearance of the Virgin by Stefano Volpi (1630), a Nativity of the Virgin by Alessandro Casolani (1585) and a reliquary of St. Catherine's relics.

They are followed by the St. Catherine Chapel, with, in the centre, an altar housing the saint's head and thumb. Il Sodoma provided an Fainting and Ecstasy of St. Catherine and Death of Niccolò di Tuldo for the chapel, while by Francesco Vanni is a St. Catherine's Exorcism (1593-1596). The 15th century marble pavement, featuring Orpheus and animals, is attributed to Francesco di Giorgio.

On the right transept is altar dedicated to Blessed Ambrogio Sansedoni, also portrayed in a canvas by Francesco Rustici (1611-612).

Notable amongst the chapels are the second, entitled to the martyrs of the German Nation, and the third, which includes a Madonna with Child and the Saint Jerome and John the Baptist by Matteo di Giovanni.